I've tried reading Regress twice now--twice! and never made it through. My brother (who has read it twice) says that it helps if you have an understanding of Lewis's life and some of the spiritual struggles he went through before coming to Christ. Regress is probably more allegorical than some of his other writings, but like in The Great Divorce, he humourously lampoons wrong thinking and leaves you with something to chew on.

Now my days are swifter than a post: they flee away ... my days are swifter than a weaver's shuttle

It is definitely worth reading - but you may find that you are like me, and are not sure about some of the philosophies the hero encounters on his definitely allegorical journey.Having the internet handy will be useful - it wasn't an option when I first read Regress.

“Stale water is a poor drink,' said Annlaw. 'Stale skill is worse. And the man who walks in his own footsteps only ends where he began.”― Lloyd Alexander, Taran Wanderer